In various industries, metal laminate structures comprising a polymeric core sandwiched between two metallic layers are used to manufacture a variety of different products. An example of such metal-polymer-metal laminates includes a constrained layer damper for the prevention and attenuation of vibration. Most constrained layer dampers, or “CLD” for short, include a very thin layer of a vibration-absorbing viscoelastic material that is disposed between and adhered to two metal-panel constraining layers. Constrained layer dampers are used in the automotive industry for vehicle body panels as well as damping inserts for automobile brake systems to diminish the propagation of structure-borne noise and the transmission of airborne noise.
In conventional practice, metal laminate structures are joined to other metal structures by riveting, bolting, or welding the two work pieces together. Welding is a manufacturing process that bonds materials, usually metals or thermoplastics, by causing coalescence—the process by which two separate units grow together, fuse, or merge into a single body. The work pieces are joined by liquefying or plasticizing (softening without liquefying) the areas to be bonded together, generally through the application of heat and/or pressure, and adding a filler material to form a localized pool of molten material (the “weld puddle”). Promoting coalescence of the liquefied or plasticized materials, and subsequently allowing the coalesced materials to cool will solidify the bond. Welding can be used, for example, to join two or more work pieces, or for operating on a single work piece (e.g., to repair a crack or join two ends together).
The quality of a weld is predominantly gauged by its strength and the strength of the material around it. Weld quality is influenced by various factors, the most influential factor being the method of welding. One such method is gas metal arc welding (GMAW), sometimes referred to by its subtypes metal inert gas (MIG) welding or metal active gas (MAG) welding. In GMAW, a continuous and consumable wire electrode and a shielding gas, typically inert, are fed through a welding gun. An electrical arc is struck between this electrode and the work piece(s) to be welded. The filler metal wire supplies the electric current to maintain the arc, which is shielded from the access of air by the shielding gas. The feed wire electrode is continuously fed towards the work piece(s), and consumed by melting under the intense heat of the arc. The metal of this electrode deposits on the base material thus forming the weld.
Gas metal arc welding has been utilized as a welding process for welding metal laminates with arguably mixed results. Laminated metal structures have heretofore been welded with GMAW using solid wire filler metal. The solid wire filler requires increased welding parameters, such as increased welding voltage and welding current, to melt the entire cross-section of the wire. The higher weld current results in increased weld porosity and melt through, both of which are undesirable welding defects. Using a solid wire electrode may also cause the arc to have turbulent, violent characteristics, which is known in the art as “sputter”.